Artificial heart valves preferably should last at least ten years in vivo. To last that long, artificial heart valves should exhibit sufficient durability for at least four hundred million cycles or more. The valves, and more specifically heart valve leaflets, must resist structural degradation including the formation of holes, tears, and the like as well as adverse biological consequences including calcification and thrombosis.
A variety of polymeric materials has previously been employed as prosthetic heart valve leaflets. Failure of these leaflets due to stiffening and hole formation occurred within two years of implant. Efforts to improve leaflet durability by thickening the leaflets resulted in unacceptable hemodynamic performance of the valves, that is, the pressure drop across the open valve was too high.
As such, it remains desirable to provide a biocompatible artificial heart valve design that lasts beyond ten years in vivo by exhibiting sufficient durability for at least about four hundred million cycles of flexure or more.
Delamination is a potential concern for synthetic prosthetic heart valve leaflets. During the cardiac cycle, a heart valve leaflet is subjected to a range of stresses arising from bending. Particular portions of the leaflet are exposed to bending that can result in splits or voids that form in the leaflet. Delamination of the leaflet can lead to failure of the leaflet in the in-vivo environment. When the leaflet delaminates, a potential space is produced into which blood elements can penetrate. Blebs of fluid, or even thrombus, can affect leaflet motion, can calcify, can affect valve function, and ultimately lead to premature valve failure.
There is a continued need in the art to address the means to improve the delamination resistance of synthetic heart valve leaflets.